docs: def cumulative_value(self, slip_moment, mmax, mag_value, bbar, dbar):
          '''
          Returns the rate of events with M > mag_value
  
          :param float slip_moment:
              Product of slip (cm/yr) * Area (cm ^ 2) * shear_modulus (dyne-cm)
          :param float mmax:
              Maximum magnitude
          :param float mag_value:
              Magnitude value
          :param float bbar:
              \bar{b} parameter (effectively = b * log(10.))
          :param float dbar:
              \bar{d} parameter
          '''
          delta_m = mmax - mag_value
          a_2 = self._get_a2(bbar, dbar, slip_moment, mmax)
          return a_2 * (np.exp(bbar * delta_m) - 1.) * (delta_m > 0.0)